Field of the Invention
The invention relates to a device for collecting and cooling core melt from a reactor pressure vessel (RPV). It is, in particular, usable in the case of an EPR pressurized water reactor.
German Published, Non-Prosecuted Patent Application DE 43 19 094 A1, corresponding to International Publication WO 94/29876 and U.S. application Ser. No. 08/569,676, filed Dec. 8, 1995, now U.S. Pat. No. 5,867,548, discloses a device for collecting and cooling core melt from an RPV, in which a prechamber that is connected through a channel to a spreading chamber, is disposed below the RPV. On the reactor side, the channel has a barrier wall or separating wall which is destroyed by the core melt within a predetermined time after the core melt has arrived. The prechamber is constructed approximately frustoconically and is bounded at the bottom by a refractory concrete base which serves somewhat as a crucible. The concrete base should be made of a refractory ceramic or special bricks. In that case, when the material alloys with the core melt the effect of the material is preferably to reduce the melting point, with the result that it makes the core melt less viscous. The bottom of the spreading chamber is lined with a heat-resistant material.
German Patent DE 43 06 864 C2 discloses a safety configuration for a nuclear reactor, in which a collection device for the core melt is disposed below the reactor pressure vessel. In that case the collection vessel is a structure made of cast elements of cast iron and/or cast steel, which forms an outflow system for the core melt. The collection device in that case corresponds, in comparison to the above-mentioned prior art, to the spreading chamber located therein, which is disposed laterally next to the RPV in that device. In that configuration, no prechamber is provided. The purpose of the collection device is clearly to cool the collected core melt in an accumulation chamber. In the case of a core melt gradually flowing downwards, plugging of the supply channels can possibly occur as a result of excessive cooling. Additional cooling is prevented in that way, as a result of which further damage can possibly occur. German Published, Prosecuted Patent Application DE-AS 22 34 782 discloses a reactor core vessel, in which a receptacle for collecting the core in the event of a core meltdown is disposed below fuel elements. In order to provide cooling, the receptacle is constructed in such a way as to be ribbed in the manner of a heat sink on the side remote from the core and is in contact with the water of a coolant circuit. The core melt can be cooled in this way. The receptacle is disposed inside the RPV in this case.